Slope spectroscopy standards
The present invention relates generally to a slope spectroscopy standards and methods of making slope spectroscopy standards, specifically standards and methods of developing standards specifically for variable pathlength (slope) measurements.
1. A method for determining a state of fitness of a spectrophotometer comprising:
testing the spectrophotometer by
measuring absorbance values for a predetermined concentration of a standard at a predetermined wavelength and multiple pathlengths using variable path length spectroscopy;
calculating a slope value of the standard from a linear regression of the absorbance values at the multiple pathlengths;
comparing the calculated slope value to a certified slope value or to the corresponding slope value on a standard curve to determine the state of fitness of the spectrophotometer,
wherein the standard is a methylxanthine or a compound selected from the group consisting of NaCl, KHP, KCl and KCr 2 O 4 .
2. The method of claim 1 , wherein the standard is in an aqueous solution.
3. The method of claim 1 , wherein the standard has a slope measurement of from about 0.01 mm to 500 mm.
4. The method of claim 1 , wherein the standard has a slope measurement of from about 1 to 500 mm.
5. The method of claim 1 , wherein the standard is a methylxanthine.
6. The method of claim 5 , wherein the methylxanthine is selected from the group consisting of caffeine, aminophylline, IBMX, paraxanthine, pentoxifylline, theobromine, and theophylline.
7. The method of claim 5 , wherein the methylxanthine is caffeine.
8. The method of claim 1 , wherein the standard has an uncertainty value of from about 0.1% to about 5%.
9. The method of claim 1 , wherein the standard has an uncertainty value of less than 1%.
10. The method of claim 1 , wherein the standard has an uncertainty value of between 0.05% and 10%.
11. The method of claim 1 , wherein the standard comprises caffeine and a compound selected from the list consisting of a colorant, a plurality micro-beads and an off peak absorber.
12. A method for determining a state of fitness of a spectrophotometer comprising:
testing the spectrophotometer by
measuring absorbance values for a predetermined concentration of a standard at a predetermined wavelength and multiple pathlengths using variable path length spectroscopy;
comparing the measured absorbance values at the multiple pathlengths to a predetermined linear regression of the standard and determining the correlation between the measured values and the predetermined values to determine the state of fitness of the spectrophotometer;
wherein the standard is a methylxanthine or a compound selected from the group consisting of NaCl, KHP, KCl and KCr 2 O 4 .
13. The method of claim 12 , wherein the standard is a compound that when measured at a given wavelength, creates a change in absorbance at different path lengths and for which a slope of a regression line can be generated.
14. The method of claim 12 , wherein the standard is in an aqueous solution.
15. The method of claim 12 , wherein the standard has a slope measurement of from about 0.01 mm to 500 mm.
16. The method of claim 12 , wherein the standard is a methylxanthine selected from the group consisting of caffeine, aminophylline, IBMX, paraxanthine, pentoxifylline, theobromine, and theophylline.
17. The method of claim 12 , wherein the standard has an uncertainty value of between 0.05% and 10%.
18. The method of claim 12 (missing), wherein the standard comprises caffeine and a compound selected from the list consisting of a colorant, a plurality micro-beads and an off peak absorber.